Bought a dedicated .22 LR AR upper from brand X to use as a rimfire suppressor host. I purchased it on the EE from a dealer of brand X's products with 1,000+ 100% positive feedback. Upper arrived and appeared unfired and in fact in new condition. I put ~50 rounds of .22 LR through it unsuppressed to sight it in, cleaned it, and put it away.

Fast forward to today, my first opportunity to shoot it suppressed. Well, it took 2 of us and the upper in a vice block to get the flash hider off. I've never had a flash hider torqued on so tightly. No residual on the threads to lead me to believe that it had thread locker, Rocksett, or any other similar product on it. Just torqued on there like crazy. Assembled this way from the factory? Swapped by the EE seller? Regardless, the threads are toast and there's no way my can will thread past the damage or I'd risk getting it stuck on there.

Attached File


Attached File


I've e-mailed the photos and this information to brand X, who has been very receptive in the past in my dealings with them. However, I don't know if they will warranty this since it was purchased from a 3rd party and it would be easy to displace the blame?

My main question is this: Are these threads salvageable? Is this a simple job for a gunsmith? Never had to deal with damage to threads before. If so, what does a job like this cost as your average gunsmith and is there any concern about barrel concentricity after a repair?

How long is the barrel and how long is the threaded portion?

Easiest fix is to cut and rethread, IF the barrel is long enough.

The way the front of those threads look (crushed) they can (maybe) be cleaned up, or removed, so something can be threaded past the damaged area.

Shouldn't hurt concentricity but, will allow carbon to build up behind the muzzle if the threads are shortened below minimum spec.

Joat

Just measured. The barrel is 16.25" from a closed bolt to the current muzzle. Crushed section is probably only ~0.25" but that's obviously too close for comfort. No options for a pinned muzzle device, since its a direct thread rimfire can.

Sent an e-mail to a local gunsmith and he told me to bring it in to look at. I'll go that route if brand X doesn't want to play ball.

Final option would be to just cut it down, rethread it, and use it on a pistol lower.

I’d chase the threads with a die before I cut anything off if the manufacturer won’t help.

Then decide.

Some threads are the same as lug studs and split dies can be used by clamping them on the good portion then turning it off the end. Cleans the right up. Unfortunately the dies are 4x the cost of the normal ones. A good machinist could split a regular one and get decent results.

In the days of bespoke hand work, a thin triangular file was used to actually make threads. Chasing them with one can be done with a steady hand to clean them up. Done it when I couldn't justify the high cost of a split die on a Subaru. It worked.

Keep in mind a barrel is not heat treated but left soft as rapid firing would pull the temper. So when torqued excessively the threads will stretch and strip more easily than expected. Same issue with torquing the barrel nut, it's not "to" 85 foot pounds, its "don't exceed" 85 foot pounds - to prevent stripping the threads on the aluminum nose. They have a low limit.

With assembled guns it's not expected too often the owner will take it apart. And things like stripped threads remain hidden for decades.

DITTO THIS^^^^^^^^^^

Contact adco firearms.  They can repair some thread eff ups.

As a retired machinist, I would either try using a split die or chucking the barrel in a lathe and using a triangle file to clean the threads up. If I did it with a lathe and file, I would run the lathe in reverse so that the file starts on teh good threads and works out towards the end of the barrel and the bad threads.

I'd like to know who told you that fairytale? Every barrel I've come across pistol or rifle had been heat treated.

ADCO

Similar thing happened to me, I chased the threads with a die. Problem solved

I think maybe there is a little misapplication of terminology and understanding here.

Generally when people hear "heat treated" they think "hardened". Heat treatment can mean anything, hardening, stress relieving, and annealing just to name a few.

The heat treatment barrels undergo, while it is technically a hardening process, isn't necessarily to gain hardness. It is to normalize & stress relieve the material and give it a certain grain structure. The result is a hardness only a small but above the annealed (dead soft) hardness. The hardness of most barrels is around 26-29 HRC which is very soft in the material properties world.

If your typical chrome-moly steel barrel were to get near 40 HRC the risk of failure through stress cracking would be greatly increased.

Just to give perspective, 13 HRC is annealed for 4150, barrels are typically 28 HRC, steel is still fairly easily machined at 62 HRC, even though 4150 can't even be hardened that hard. So barrels are still very soft so that they aren't brittle.

This^

I had a local gunsmith do just this. Problem solved. Thanks for the input, gentlemen.